Question 1

Which of the following statements best describes a chemical element?

Accepted Answer

A substance made of only one type of atom.

Question 2

Which six elements make up approximately 97% of the mass of most living organisms?

Accepted Answer

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

Question 3

An atom of oxygen has an atomic number of 8 and a mass number of 16. How many neutrons does it have?

Accepted Answer

$$16 - 8 = 8$$

Question 4

Which subatomic particle determines the atomic number of an element?

Accepted Answer

Proton

Question 5

What is the total number of electrons in a neutral atom of phosphorus ($$^{31}_{15}P$$)?

Accepted Answer

$$15$$

Question 6

According to the octet rule, how many electrons are needed in the valence shell of most atoms to achieve stability?

Accepted Answer

$$8$$

Question 7

Which of the following best explains why neon (Ne) is chemically unreactive?

Accepted Answer

Its valence shell is full.

Question 8

How many valence electrons does a neutral atom of oxygen have?

Accepted Answer

$$6$$

Question 9

Which of the following statements about electron shells is TRUE?

Accepted Answer

Shells closer to the nucleus are lower in energy.

Question 10

A carbon atom has 6 protons, 6 neutrons, and 6 electrons. What is its atomic mass?

Accepted Answer

$$6 + 6 = 12$$

Question 11

Which of the following is a trace element required in small amounts for life?

Accepted Answer

Iron (Fe)

Question 12

If an atom has 11 protons, 12 neutrons, and 11 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number: $$11$$, Mass number: $$23$$

Question 13

Which of the following best describes the relationship between matter, chemical elements, and atoms?

Accepted Answer

Matter is made of chemical elements, which are made of atoms.

Question 14

Which of the following is the correct electron configuration for a neutral nitrogen atom (atomic number 7)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^3$$

Question 15

A neutral atom of sulfur has 16 electrons. How many electrons are in its outermost shell?

Accepted Answer

$$6$$

Question 16

Which of the following is true about the periodic table?

Accepted Answer

It arranges elements based on their chemical properties.

Question 17

If an atom has a full outermost electron shell, it is most likely to:

Accepted Answer

Be chemically unreactive.

Question 18

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 19

Which of the following best explains why carbon is essential for life?

Accepted Answer

It can form four covalent bonds, allowing for complex molecules.

Question 20

A neutral atom of sodium ($$^{23}_{11}Na) $$loses one electron. What is the resulting charge?

Accepted Answer

$$+1$$

Question 21

Which of the following is true about valence electrons?

Accepted Answer

They are found in the outermost electron shell and determine chemical reactivity.

Fundamentals of Atomic Structure and Elements in General Chemistry

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